Comparability of gene expression between human and baboon CD34+ marrow cells

Abstract Nonhuman primates are a useful model system for hematopoietic stem cell (HSC) research because they are closely related to humans. We asked whether human-based cDNA arrays could be used to study hematopoiesis in the baboon. Our objective was to compare the human and baboon transciptosome, using cDNA filter arrays surveying 25,920 human genes (Unigene), to determine if the expression patterns were similar, and to identify the commonly-expressed genes. Bone marrow mononuclear cells from a normal adult human and an adult baboon were sorted using magnetic beads, to obtain CD34+ cells of 90% and 77% purity, respectively. Total RNA was 33 P-labeled by oligo-dT primed reverse-transcription, hybridized sequentially in the presence of human Cot1 DNA and poly dA to GeneFilters releases 200–204 (Research Genetics), phospho-imaged and analyzed with Pathways software. The baboon-derived probes had a slightly higher background than human (3-fold) so the expression of low abundance cDNAs was less reliable. Overall, the relative expression of individual genes was comparable between the species, with a correlation coefficient which varied by experiment, but was between 0.86–0.90. A total of 5,474 genes showed comparably high expression in both species (≥ 10-fold above baseline) of which 1,123 were ≥ 100-fold. These highly-expressed cDNAs (67 genes, 956 ESTs) included genes such as IL-3 receptor, HLA class II, and CSF3 receptor. Only a few genes/ESTs showed species-restricted expression (75 in human and 59 in baboon). We conclude that human cDNA arrays are a reliable method to study baboon marrow. The genes/ESTs identified here represent a useful set for generating a cDNA microarray chip to study baboon stem cell function, which will facilitate the study of HSC gene expression during steady state hematopoiesis and following a variety of stimuli.